Wireless power conversion (WPC) is a non-contact charging technology which is a wireless charging technology in which a battery is charged using magnetic coupling without electrical contact at a short distance.
According to transmission standards of WPC, a technique by which predetermined signals are periodically transmitted from a transmitter to a receiver to detect whether the receiver is located in an area which the transmitter can reach, is used. A battery can be charged using magnetic coupling without an additional electrical contact in WPC, and as such WPC can be applied to battery charging in various fields.
Meanwhile, a hall sensor is mounted on a transmitter that transmits power in transmission standards for power matters alliance (PMA), and the hall sensor detects the instant that a receiver is located in an area which the transmitter can reach, such that a consumption of standby power is small.
In such a WPC or PMA technique, a magnetic field is formed by alternating current (AC) power energy generated in a primary coil, current flows through a coil of an antenna, and a voltage is generated due to an inductance of the antenna. The voltage generated in this way is used as power for data transmission or to charge a battery.
However, in the PMA technique, in order for the hall sensor of the transmitter to detect the receiver, a difference of a predetermined gauss or more has to be generated when the receiver is located in an area which the transmitter can reach, and a voltage difference of a predetermined voltage or more has to be generated when the receiver is not located in an area which the transmitter can reach.
Such a voltage difference is mostly affected by a thickness of a shielding material of the receiver. In order to form a voltage difference of a predetermined voltage or more, the thickness of the shielding material has to be large. Thus, material costs increase and it becomes difficult to embed the receiver in a portable mobile terminal device due to the thickness of the shielding material.